Erasable ink for a writing implement

ABSTRACT

At least one embodiment of the present invention relates to an erasable ink composition particularly useful in a writing instrument for simultaneous the appearance of a graphite pencil. The composition of the present invention comprises a solvent system, a rubber and a pigment. The solvent system used in the present invention comprises an organic ester and a component selected from the group consisting of an optionally substituted cycloalkane, an optionally substituted cycloalkanone, an optionally substituted cycloalkene, or mixtures thereof. A sufficient amount of the solvent system is present so that the erasable ink composition will flow in a writing instrument. Preferably, the erasable ink composition of the present invention includes a pigment comprising graphite and carbon black. Finally, the erasable ink composition optionally includes a plasticizer, a liquid butene, or one or more additives selected from the group consisting of a corrosion inhibitor, a flow enhancing compound, and mixtures thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 371U.S. National phase entry of InternationalPatent Application PCT/US04/00385 filed on Jan. 9, 2004, which is acontinuation-in-part of U.S. application Ser. No. 10/339,485, filed Jan.9, 2003, now issued as U.S. Pat. No. 6,890,972.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In at least one aspect, the present invention is related to erasable inkcompositions that substantially simulate the appearance of a graphitepencil, and more particularly to erasable ink compositions thatsubstantially simulate the appearance of a graphite pencil and aresuitable for use in replaceable cartridges.

2. Background Art

For a number of years, there has been a desire to produce a pen thatproduces an erasable, pencil-like trace. Although a number of erasableink compositions are known, attempts to make erasable ink compositionsthat substantially simulate the trace of a pencil have been plagued bydifficulties related to the poor quality of the trace produced and topoor erasability. Notwithstanding the problems associated with thepencil-simulating compositions, ink compositions that are erasable witha typical pencil eraser are known. Generally, such compositions maintainerasability for at least several hours.

The erasable ink prior art includes erasable ink compositions that areboth water-based and non-water based. The non-water based erasable inkformulations minimally contain a rubber, a pigment, and at least onesolvent. For example, U.S. Pat. Nos. 4,390,646 and 4,389,499, eachdisclose an erasable ink composition which includes a thermoplasticblock copolymer, pigments, and a solvent. Preferably the copolymers area mixture of radial and linear block copolymers. Similarly, U.S. Pat.No. 4,721,739 (the '739 patent) discloses an erasable ink compositionthat contains a block polymer, a plasticizer, a lubricant, a colorant(i.e., a pigment), and a resin. Suitable plasiticizers as set forth inthe '739 patent are aliphatic esters such as butyl stearate and dioctyladipate; or aromatic esters such as dioctyl phthalate. These esters havea moderate molecular weight that is greater than 250.

The particular choice of pigments is important in maintaining theerasability of traces formed by the erasable ink composition. Moreover,the selection of an appropriate rubber (block polymer) dissolved in asolvent is such that when the solvent evaporates the ink viscosityincreases to the point where further penetration of the ink to the paperis minimized. Unfortunately, these compositions are often plagued byclogging of the writing implement (i.e., the pen) over extended periodsof time of non-use. This phenomenon tends to be somewhat worse when theink is exposed to a humid environment. Accordingly, U.S. Pat. No.4,629,748 (the '748 patent) provides at least a partial solution to thisproblem by disclosing the utility of various dispersants in erasable inkcompositions which contain rubber and non-aqueous solvents.Specifically, the '748 demonstrates the use of alkyl phosphate ester,amines, and oxyethylene-oxypropylene block copolymers.

Similarly, numerous water-based erasable ink compositions exist in theprior art. Typically, such aqueous compositions include a blockcopolymer such as styrene-butadiene and a pigment. Generally suchcompositions also include one or more additives such as releasing andspreading agents, antioxidants, surfactants, gelatinizers, lubricants,and various waxes.

Although many of the various prior art erasable ink compositionsgenerally work to some degree, there is still a need for an improvederasable ink composition that produces tracings that substantially mimicthe tracings of a pencil without substantially clogging the writingimplement and without substantial breaks in the formed tracings.Moreover, there is also a need for a formulation that is capable ofproducing tracings that are for erasable for one or more days instead ofthe few hours which is typical of the prior art formulations.

SUMMARY OF THE INVENTION

The present invention overcomes at least one of the problems encounteredin the prior art by providing an improved erasable ink compositionparticularly useful in a writing instrument that produces tracingssubstantially similar in appearance to tracings formed by a graphitepencil. Moreover, the composition of the present invention producestracings that are substantially erasable with a common rubber pencilerasable for at least one day after the tracings are formed on paper. Inat least one embodiment, the composition of the present inventioncomprises a solvent system, a rubber, and a pigment. The solvent systemused in the present invention includes an organic ester and a componentselected from the group consisting of an optionally substitutedcycloalkane, an optionally substituted cycloalkanone, an optionallysubstituted cycloalkene, or mixtures thereof. The composition contains asufficient amount of the solvent system so that the erasable inkcomposition will flow in a writing instrument. Finally, the erasable inkcomposition of the present invention optionally include one or more ofthe following:

a plasticizer

an additive selected from the group consisting of a corrosion inhibitor,a flow enhancing compound, and mixtures thereof; and

a liquid butene polymer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferred compositionsor embodiments and methods of the invention, which constitute the bestmodes of practicing the invention presently known to the inventors.

Except in the claims and the operating examples, or where otherwiseexpressly indicated, all numerical quantities in this descriptionindicating amounts of material or conditions of reaction and/or use areto be understood as modified by the word “about” in describing thebroadest scope of the invention. Practice within the numerical limitsstated is generally preferred. Also, unless expressly stated to thecontrary: percent, “parts of”, and ratio values are by weight; the term“polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like;the description of a group or class of materials as suitable orpreferred for a given purpose in connection with the invention impliesthat mixtures of any two or more of the members of the group or classare equally suitable or preferred; description of constituents inchemical terms refers to the constituents at the time of addition to anycombination specified in the description, and does not necessarilypreclude chemical interactions among the constituents of a mixture oncemixed; specification of materials in ionic form implies the presence ofsufficient counter-ions to produce electrical neutrality for thecomposition as a whole (any counter-ions thus implicitly specifiedshould preferably be selected from among other constituents explicitlyspecified in ionic form, to the extent possible; otherwise suchcounter-ions may be freely selected, except for avoiding counter-ionsthat act adversely to the objects of the invention); and the term “mole”and its variations may be applied to elemental, ionic, and any otherchemical species defined by number and type of atoms present, as well asto compounds with well defined molecules.

The term “cycloalkane” as used herein refers to cyclic saturatedhydrocarbons having a ring of carbon atoms. A cycloalkane may besubstituted with one or more substituents (i.e., optionallysubstituted.) Suitable substituents include, but are not limited to,lower alkyl, lower alkoxy, lower thioalkoxy, hydroxy, lower alkyl amino,amino, and nitro.

The term “cycloalkene” as used herein refers to cyclic hydrocarbonshaving a ring of carbon atoms with one or more double bonds. Acycloalkene may be substituted with one or more substituents (i.e.,optionally substituted.) Suitable substituents include, but are notlimited to, lower alkyl, lower alkoxy, lower thioalkoxy, hydroxy, loweralkyl amino, amino, and nitro.

The term “cycloalkanone” as used herein refers to cyclic saturatedhydrocarbons having a ring of carbon atoms where at least one of thecarbon atoms of the ring is doubly bonded to oxygen. A cycloalkanone maybe substituted with one or more substituents (i.e., optionallysubstituted.) Suitable substituents include, but are not limited to,lower alkyl, lower alkoxy, lower thioalkoxy, hydroxy, lower alkyl amino,amino, and nitro.

The term “lower alkyl” as used herein refers to a branched or straighthydrocarbon radical having from 1 to 6 carbon atoms and includes forexample, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, and the like.

The term “lower alkoxy” as used herein refers to O-alkyl of from 1 to 6carbon atoms as defined above for “lower alkyl.”

The term “thioalkoxy” as used herein refers to S-alkyl of from 1 to 6carbon atoms as defined above for “lower alkyl.”

The term “halogen” as used herein refers to fluorine, chlorine, bromine,or iodine.

The term “organic ester” as used herein refers to organic compoundsformed by the reaction of a carboxylic acid and an alcohol.

The term “phosphate ester” as used herein refers to compounds formed bythe reaction of phosphoric acid (H₃PO₄) and an alcohol. Included in thisdefinition are compounds formed by the replacement of one, two, or threehydroxyl groups in phosphoric by alkoxyl.

The term “phthalic ester” as used herein means an ester of phthalicacid. Phthalic esters are often made by reacting phthalic anhydride withan alcohol in the presence of sulfuric acid.

In an embodiment of the present invention, an erasable ink compositionis provided. The erasable ink composition comprises:

a solvent system including:

a component selected from the group consisting of an optionallysubstituted cycloalkane, an optionally substituted cycloalkene, anoptionally substituted cycloalkanone, and mixtures thereof; and

an organic ester;

rubber; and

a pigment;

wherein a sufficient amount of the solvent system is added so that theerasable ink composition will flow in a writing implement. Typically,the erasable ink composition of the present invention will be providedin a reusable cartridge with the ink under a pressure from 15 psi to 20psi. The solvent system is present in a sufficient amount so that theerasable ink composition has a viscosity from 20,000 cP to 60,000 cP at25° C. More preferably, the solvent system is present in a sufficientamount that the erasable ink composition has a viscosity from 30,000 cPto 50,000 cP at 25° C.; and most preferably the solvent system ispresent in a sufficient amount that the erasable ink composition has aviscosity of 40,000 cP at 25° C. The compositions of the presentinvention produces tracings that are substantially erasable with acommon rubber pencil erasable for at least one day after the tracingsare formed on paper. Moreover, the compositions of the present inventionproduces tracings that are substantially erasable with a common rubberpencil erasable for a week or longer after the tracings are formed onpaper.

The erasable ink composition of the present invention optionallyincludes one or more of the following:

a plasticizer

an additive selected from the group consisting of a corrosion inhibitor,a flow enhancing compound, and mixtures thereof; and

a liquid butene polymer.

Many of the improved features of the present invention are attributableto the selection of the solvent system. The solvent system comprises acyclic component selected from the group consisting of an optionallysubstituted cycloalkane, an optionally substituted cycloalkanone, andmixtures thereof; and an organic ester. In certain embodiments, thecyclic component is selected from the group consisting of optionallysubstituted cycloalkane having a 4 to 7 member ring, an optionallysubstituted cycloalkanone having a 4 to 7 member ring, an optionallysubstituted cycloalkene having a 4 to 7 member ring, and mixturesthereof. In other embodiments, the cyclic component is selected from thegroup consisting of cyclohexane, cyclohexanone, and mixtures thereof;and in certain preferred embodiments the cyclic component iscyclohexane. In certain embodiments, the organic ester is a lowmolecular weight organic ester with a molecular weight that is less than250. In other embodiments, the organic ester has a molecular weight lessthan 200. In certain preferred embodiments, the organic ester isisobutyl butyrate.

As set forth above, in certain embodiments, the solvent system ispresent in a sufficient amount such that the erasable ink compositionhas a viscosity from 20,000 cP to 60,000 cP at 25° C. Viscosity valuesin this range are typically obtained when the solvent system is presentin an amount of 25% to 55% of the total weight of the erasable inkcomposition. More preferably, the solvent system is present in an amountof 30% to 45% of the total weight of the erasable ink composition; andmost preferably, the solvent system is present in an amount of 34% ofthe total weight of the erasable ink composition. All percentages of theerasable ink composition as expressed in this document, unless otherwisestated, refer to the weight percentage of the stated component relativeto the total weight of the erasable ink composition at standardtemperature and pressure. The preferred solvent system comprisescyclohexane and isobutyl butyrate. In this variation, the cyclohexane ispreferably present in an amount of 40% to 80% of the total weight of thesolvent system, and the isobutyl butyrate is preferably present in anamount of 20% to 60% of the total weight of the solvent system. Morepreferably, the cyclohexane is present in an amount of 45% to 70% of thetotal weight of the solvent system, and the isobutyl butyrate is presentin an amount of about 30% to 55% of the total weight of the solventsystem; and most preferably, the cyclohexane present in an amount of 65%of the total weight of the solvent system; and isobutyl butyrate ispresent in an amount of 35% of the total weight of the solvent system.

The composition of the present invention further comprises rubber. Bothsynthetic and natural rubber and mixtures thereof are suitably included.In certain embodiments, the rubbers are natural or synthetic rubbersthat are copolymers of styrene and isoprene. Accordingly, thesecopolymer may be block copolymers, random copolymers, graft copolymers,or mixtures thereof. Preferably, the rubber is a block copolymer andmore preferably, a block copolymer of styrene and isoprene. The rubberis preferably present in an amount of 10% to 40% of the total weight ofthe erasable ink composition. More preferably, the rubber is present inan amount of 10% to 25% of the total weight of the erasable inkcomposition; and most preferably the rubber is present in an amount of15% of the total weight of the erasable ink composition. A particularlypreferred rubber is Kraton™ D-1107 which is a styrene-isoprene-styreneblock copolymer that includes an antioxidant, a stabilizer, and dustingagents. Kraton™ D-1107 is commercially available from Kraton Polymerslocated in Houston Tex.

The erasable ink of the present invention also includes a pigment. Incertain embodiments, the pigment is a powder pigment wherein the powderparticles have an mean particle diameter of 0.05 to 4 microns. In otherembodiments, the pigment particles have a mean diameter of 0.5 to 3microns; and in certain preferred embodiments the pigment particles havea mean diameter of 2 microns. Particularly useful powdered pigmentscomprise graphite powder, carbon black, and mixtures thereof. In certainembodiments, the powdered pigment is present in an amount of 2% to 25%of the total weight of the erasable ink composition. More preferably,the powdered pigment is present in an amount of 5% to 20% of the totalweight of the erasable ink composition; and most preferably the powderedpigment is present in an amount of 18% of the total weight of theerasable ink composition. Particularly preferred pigments includegraphite and carbon black. Particularly preferred pigments are syntheticgraphite grade 4827 commercially available from Asbury Graphite millslocated in Asbury N.J. and carbon black (A148D) commercially availablefrom Clariant.

In a particularly useful variation of the present invention, the pigmentcomprises a mixture of graphite and carbon black. This combinationadvantageously provides an ink composition which exhibits less wear onthe tip (i.e., the ball) of a ballpoint pen. Though not limiting themechanism of such improved performance to any particular theory, it isbelieved that the finer particle size of carbon black as compared tographite allows such enhancement. Moreover, this combination of graphiteand carbon black also provides the desired appearance of print made fromthe erasable ink composition of the present invention. As set forthabove, the combination of graphite and carbon black is preferably fromabout 2% to 25% of the total weight of the erasable ink composition.More preferably, the combination of graphite and carbon black is presentin an amount of 5% to 20% of the total weight of the erasable inkcomposition; and most preferably the combination of graphite and carbonblack is present in an amount of 18% of the total weight of the erasableink composition. The amount of graphite is preferably from about 2% toabout 20% of the total weight of the erasable ink composition. Morepreferably, the amount of graphite is from about 10% to about 18% of thetotal weight of the erasable ink composition; and most preferably, theamount of graphite is about 14% of the total weight of the erasable inkcomposition. Similarly, the amount of carbon black is preferably fromabout 2% to about 20% of the total weight of the erasable inkcomposition. More preferably, the amount of carbon black is from about2% to about 8% of the total weight of the erasable ink composition; andmost preferably, the amount of carbon black is about 4% of the totalweight of the erasable ink composition.

The erasable ink composition of the present invention also optionallyincludes a liquid butene polymer and a plasticizer. Suitable butenepolymers include, but are not necessarily limited to, polybutene orcopolymers of butene and isobutene, and mixtures thereof. Preferably,the butene polymer is present in an amount from about 2% to about 20% ofthe total weight of the erasable ink composition. More preferably, thebutene polymer is present in an amount of about 4% to about 18% of thetotal weight of the erasable ink composition. The plasticizer ispreferably at least one phthalic ester. Preferred phthalic esterscomprise dibutyl phthalate, dioctyl phthalate, and mixtures thereof. Incertain embodiments, the plasticizer is present in an amount of 3% to25% of the total weight of the erasable ink composition. In otherembodiments, the plasticizer is present in an amount of 5% to 12% of thetotal weight of the erasable ink composition; and in certain preferredembodiments, the at least one phthalic ester is present in an amount of16% of the total weight of the erasable ink composition. In a preferredembodiment of the present invention, the at least one phthalic ester isa phthalic ester mixture comprising dibutyl phthalate in an amount of10% to 40% of the total weight of the phthalic ester mixture; anddioctyl phthalate in an amount of 60% to 90% of the total weight of thephthalic ester mixture.

The erasable ink composition of the present invention also optionallycomprises an additive selected from the group consisting of a corrosioninhibitor, dispersants, a flow enhancing material, lubricants, resins,and mixtures thereof. Preferred corrosion inhibitors, include but arenot necessarily limited to phosphate esters, and in particular to alkylphosphate esters. A suitable phosphate ester is Rhodafac RS-410commercially available from Rhodia HPCII. The corrosion inhibitor helpsprotect the metal components in the writing instrument (i.e., the pen)from the corrosive activity of the erasable ink composition. Moreover,phosphate ester may also improve dispersion of the ink over extendedperiods of time. The corrosion inhibitor is preferably present in anamount of 0.5% to 6% of the total weight of the erasable inkcomposition. More preferably, the corrosion inhibitor is present in anamount of 1% to 5% of the total weight of the erasable ink composition;and most preferably the corrosion inhibitor is present in an amount of2% of the total weight of the erasable ink composition.

Although not limiting the practice of the invention to any particularmechanism of operation, the flow enhancing materials, the lubricant, andthe resins function at least to some degree by allowing the viscosity ofthe erasable composition to be adjusted within the limits as set forthabove. Preferred flow enhancing materials include mineral oil andglycerin. Suitable mineral oils include, but are not limited to, theDrakol™ line of mineral oils available from Pennzoil and Rudol™ oilavailable from Witco Chemical Co. Preferably, the mineral oil is presentin an amount of 0.5% to 12% of the total weight of the erasable inkcomposition. More preferably, the mineral oil is present in an amount of1% to 10% of the total weight of the erasable ink composition; and mostpreferably, the mineral oil is present in an amount of 8% of the totalweight of the erasable ink composition. Similarly, the glycerin ifpresent is preferably present in an amount of about 1% to about 20% ofthe total weight of the erasable ink composition. More preferably, theglycerin is present in an amount of about 2% to about 15% of the totalweight of the erasable ink composition. The composition of the presentinvention may also include one or more lubricants. If present, thelubricants are preferably present in an amount from 0.5% to 10% of thetotal weight of the erasable ink composition. More preferably, thelubricants are present in an amount from 1% to 5% of the total weight ofthe erasable ink composition; and most preferably, the lubricants arepresent in an amount of 2% of the total weight of the erasable inkcomposition. A particularly preferred lubricant is Penetek™ commerciallyavailable from JMN Specialties, Inc. located in Westwego, La.

The erasable ink composition of the present invention may also includean additive which is a resin. Such resins when used are preferablypresent in an amount from 0.1% to 3% of the total weight of the erasableink composition. More preferably, such resins are present in an amountfrom 0. 1% to 1% of the total weight of the erasable ink composition. Apreferred resin is a polyvinylpyrrolidone such as PVPK-30™ or PVPK-90™which is commercially available from BASF Corporation located inWyandotte, Mich.

The following non-limiting examples illustrate the various embodimentsof the present invention. Those skilled in the art will recognize manyvariations that are within the spirit of the present invention and scopeof the claims.

EXAMPLE 1

The composition illustrated in Table 1 is prepared by mixing thecomponents together.

TABLE 1 Weight percentages of erasable ink composition Component Weight% cyclohexane 22 isobutyl isobutyrate 18 Kraton Polymer D-1107 20Dibutyl Phthalate 12 Dioctyl Phthalate 4 Rhodafac RS-410 3 Drakol Oil 3Polybutene 6 Graphite (Grade 4827) 12

EXAMPLE 2

The composition illustrated in Table 2 is prepared by mixing thecomponents together. The premix is made in advance by combining 95weight percent glycerin and 5 weight percent PVPK-30 prior to combiningwith the other ingredients.

TABLE 2 Weight percentages of erasable ink composition Component Weight% cyclohexane 18 isobutyl isobutyrate 13 Kraton Polymer D-1107 18Dibutyl Phthalate 5 Rhodafac RS-410 4 Drakol Oil 2 Polybutene 9 Glycerin10 Premix of 95 weight 5 percent glycerin and 5 weight percent PVPK-30Penetek 2 Graphite (Grade 4827) 14

EXAMPLE 3

The composition illustrated in Table 3 is prepared by mixing thecomponents together. The premix is made in advance by combining 95weight percent glycerin and 5 weight percent PVPK-90 prior to combiningwith the other ingredients. (Rudol™ oil may be substituted for theDrakol™ oil.)

TABLE 3 Weight percentages of erasable ink composition Component Weight% cyclohexane 22 isobutyl isobutyrate 12 Kraton Polymer D-1107 15Dibutyl Phthalate 8 Rhodafac RS-410 2.25 Drakol Oil 8 Polybutene 12Premix of 95 weight 2.75 percent glycerin and 5 weight percent PVPK-90Graphite (Grade 4827) 14 carbon black 4

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. An erasable ink composition comprising: a solvent system including: acomponent selected from the group consisting of an optionallysubstituted cycloalkane, an optionally substituted cycloalkene, anoptionally substituted cycloalkanone, and mixtures thereof; and isobutylbutyrate; a rubber; and a pigment; the solvent system present in asufficient amount that the erasable ink composition will flow in awriting implement.
 2. The erasable ink composition of claim 1 whereinthe pigment is graphite powder, carbon black powder, or mixture thereof.3. The erasable ink composition of claim 1 wherein the pigment ispresent in an amount of 2% to 25% of the total weight of the erasableink composition.
 4. The erasable ink composition of claim 1 wherein asufficient amount of the solvent system is present so that the erasableink composition has a viscosity from 20,000 cP to 60,000 cP at 25° C. 5.The erasable ink composition of claim 1 wherein the solvent systemcomprises a component selected from the group consisting of anoptionally substituted cycloalkane having a 4 to 7 member ring, anoptionally substituted cycloalkanone having a 4 to 7 member ring, anoptionally substituted cycloalkene having a 4 to 7 member ring, andmixtures thereof; and an organic ester.
 6. The erasable ink compositionof claim 1 wherein the solvent system comprises: a component selectedfrom the group consisting of cyclohexane, cyclohexanone, and mixturesthereof; and isobutyl butyrate.
 7. The erasable ink composition of claim1 wherein the solvent system is present in an amount of 25% to 55% ofthe total weight of the erasable ink composition.
 8. The erasable inkcomposition of claim 7 wherein the solvent system includes: cyclohexanepresent in an amount of 40% to 80% of the total weight of the solventsystem; and isobutyl butyrate present in an amount of 20% to 60% of thetotal weight of the solvent system.
 9. The erasable ink composition ofclaim 1 wherein the rubber is a natural or synthetic rubber.
 10. Theerasable ink composition of claim 1 wherein the rubber is a syntheticrubber which is a copolymer of styrene and isoprene.
 11. The erasableink composition of claim 1 wherein the natural or synthetic rubber is apresent in an amount of 10% to 40% of the total weight of the erasableink composition.
 12. The erasable ink composition of claim 1 furthercomprising a component selected from the group consisting of: aplasticizer; an additive selected from the group consisting of acorrosion inhibitor, a flow enhancing compound, and mixtures thereof; aliquid butene polymer; and mixtures thereof.
 13. The erasable inkcomposition of claim 12 wherein the additive comprise a corrosioninhibitor.
 14. The erasable ink composition of claim 13 wherein thecorrosion inhibitor comprises a phosphate ester present in an amount of0.5% to 6% of the total weight of the erasable ink composition.
 15. Theerasable ink composition of claim 12 wherein the additive comprises aflow enhancing material.
 16. The erasable ink composition of claim 15wherein the flow enhancing material is a mineral oil present in anamount of 0.5% to 12% of the total weight of the erasable inkcomposition.
 17. The erasable ink composition of claim 12 wherein theliquid butene polymer comprises a component selected from the groupconsisting of polybutene, a copolymer of butene and isobutene, andmixtures thereof.
 18. The erasable ink composition of claim 12 whereinthe plasticizer is at least one phthalic ester selected from the groupconsisting a dibutyl phthalate, dioctyl phthalate, and mixtures thereof.19. The erasable ink composition of claim 18 wherein the at least onephthalic ester is present in an amount of 3% to 25% of the total weightof the erasable ink composition.
 20. The erasable ink composition ofclaim 18 wherein the at least one phthalic ester is a phthalic estermixture comprising: dibutyl phthalate in an amount of 10% to 40% of thetotal weight of the phthalic ester mixture; and dioctyl phthalate in anamount of 60% to 90% of the total weight of the phthalic ester mixture.21. An erasable ink composition comprising: a solvent system including:a component selected from the group consisting of an optionallysubstituted cycloalkane, an optionally substituted cycloalkene, anoptionally substituted cycloalkanone, and mixtures thereof; and isobutylbutyrate; at least one phthalic ester selected from the group consistinga dibutyl phthalate, dioctyl phthalate, and mixtures thereof; a rubber;an additive selected from the group consisting of a corrosion inhibitor,a flow enhancing compound, and mixtures thereof; a liquid butenepolymer; and a pigment comprising graphite and carbon black.
 22. Theerasable ink composition of claim 21 wherein the solvent system presentin a sufficient amount that the erasable ink composition will flow in awriting implement and the erasable ink composition has a viscosity from20,000 cP to 60,000 cP at 25° C.
 23. The erasable ink composition ofclaim 21 wherein the solvent system comprises a component selected fromthe group consisting of an optionally substituted cycloalkane having a 4to 7 member ring, an optionally substituted cycloalkanone having a 4 to7 member ring, an optionally substituted cycloalkene having a 4 to 7member ring, and mixtures Thereof; and an organic ester.
 24. Theerasable ink composition of claim 21 wherein the solvent systemcomprises: a component selected from the group consisting ofcyclohexane, cyclohexanone, and mixtures thereof; and isobutyl butyrate.25. The erasable ink composition of claim 21 wherein the solvent systemis present in an amount of 25% to 55% of the total weight of theerasable ink composition.
 26. The erasable ink composition of claim 21wherein the graphite is present in an amount of about 2% to about 20% ofthe total weight of the erasable ink composition and the carbon black ispresent in an amount of about 20% to about 20% of the total weight ofthe erasable ink composition.
 27. An erasable ink compositioncomprising: a solvent system including: cyclohexane present in an amountfrom about 40% to about 80% of the total weight of the solvent system;and isobutyl butyrate present in an amount from about 20% to about 60%of the total weight of the solvent system; at least one phthalic esterselected from the group consisting a dibutyl phthalate, dioctylphthalate, and mixtures thereof; a rubber; an additive selected from thegroup consisting of a corrosion inhibitor, a flow enhancing compound,and mixtures thereof; a liquid butene polymer; and a pigment comprisinggraphite and carbon black; the solvent system present in a sufficientamount that the erasable ink composition will flow in a writingimplement and the erasable ink composition has a viscosity from 20,000cP to 60,000 cP at 25° C.
 28. The erasable ink composition of claim 27wherein the solvent system is present in an amount of 25% to 55% of thetotal weight of the erasable ink composition.